New dumb-bell-typefullerene adducts 2, 4, and 8a–b could be synthesized via bifunctional nitrile oxides. The [60]fullerene derivative 16 of this type was synthesized by twofold esterification with an isoxazolo[60]fullerenecarboxylic acid derivative. In the latter case the reaction was used to link the archimedic polyhedron fullerene with the platonic element cubane. When a bulky spacer between the
Bent bonds in the strained fullerene system, restricted to the [5,6] bonds, were detected by high-resolution X-ray structure analysis of the 1,2-dihydro[60]fullerene derivative 1. In addition the maxima of electron densities are higher in the [6,6] bonds than in the [5,6] bonds-an important finding with respect to the question of the extent of electron delocalization in fullerenes.